U.S. patent number 3,941,003 [Application Number 05/486,775] was granted by the patent office on 1976-03-02 for balanced sickle drive.
This patent grant is currently assigned to Hesston Corporation. Invention is credited to Cecil L. Case, Harold Keith Garrison, Allen A. White.
United States Patent |
3,941,003 |
Garrison , et al. |
March 2, 1976 |
Balanced sickle drive
Abstract
A sickle drive has a sway bar that is coupled with the sickle to
reciprocate the latter during oscillation of the sway bar. The
latter is operably coupled with a crank drive through a special
linkage employing a pair of oppositely extending, short pitman
links that compensate for one another adjacent opposite ends of the
sickle stroke to vary the velocity of the sickle substantially
sinusoidally. The oppositely directed inertia forces of the sickle
adjacent opposite ends of its stroke, made equal by the special
linkage, are balanced out by a pair of superimposed, oppositely
rotating weights driven in timed relationship to reciprocation of
the sickle, thereby presenting a substantially vibration-free
drive.
Inventors: |
Garrison; Harold Keith (Newton,
KS), Case; Cecil L. (Newton, KS), White; Allen A.
(Peabody, KS) |
Assignee: |
Hesston Corporation (Hesston,
KS)
|
Family
ID: |
23933194 |
Appl.
No.: |
05/486,775 |
Filed: |
July 9, 1974 |
Current U.S.
Class: |
74/44;
56/296 |
Current CPC
Class: |
A01D
34/30 (20130101); Y10T 74/18208 (20150115) |
Current International
Class: |
A01D
34/02 (20060101); A01D 34/30 (20060101); F16H
021/22 () |
Field of
Search: |
;56/296 ;74/44,25 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; Samuel
Assistant Examiner: Ratliff, Jr.; Wesley S.
Attorney, Agent or Firm: Schmidt, Johnson, Harvey &
Williams
Claims
Having thus described the invention, what is claimed as new and
desired to be secured by Letters Patent is:
1. In apparatus for translating rotary motion into reciprocal
motion:
a rotary drive shaft;
a single component eccentrically coupled with said shaft for
orbital movement about the axis of the shaft when the latter is
rotated,
said component being pivotal about a second axis during said
orbiting movement;
a reciprocable member; and
structure coupling said member with said component,
said structure being pivotally connected to said component at a
pair of spaced points on opposite sides of said second axis for
reciprocating the member during rotation of said shaft.
2. In apparatus as claimed in claim 1, wherein said structure is
disposed to limit said component to its own rectilinear path of
reciprocation relative to said member during rotation of said
shaft.
3. In apparatus as claimed in claim 2, wherein said path of the
component is transverse to the path of the member.
4. In apparatus as claimed in claim 3, wherein said structure
includes a pair of swingable connectors between said member and the
component on opposite sides of said second axis.
5. In apparatus as claimed in claim 4, wherein said connectors
extend in opposite directions from said component.
6. In apparatus as claimed in claim 5, wherein said member is
provided with an opening, said connectors disposing said component
for reciprocation within said opening.
7. In apparatus for translating rotary motion into reciprocal
motion:
a rotary drive shaft;
a reciprocable member;
a single component coupled with said member in a manner to limit
movement of the component relative to the member to rectilinear
reciprocation transversely of the path of travel of the member;
and
means eccentrically and pivotally coupling said component with the
shaft for orbital movement about the axis of the shaft when the
latter is rotated, whereby to drive said member along said
path.
8. In apparatus as claimed in claim 7, wherein said member is
coupled with said component on opposite sides of the pivotal axis
of the component.
9. In apparatus as claimed in claim 8, wherein said component is
provided with a pair of oppositely extending, swingable connectors
on opposite sides of its pivotal axis and joining the component
with said member.
10. In apparatus as claimed in claim 9, wherein said member is
provided with a sickle for reciprocating the latter during
reciprocation of the member.
11. In apparatus as claimed in claim 10, wherein said member is
swingable along said path about an axis spaced from said
sickle.
12. In apparatus as claimed in claim 11, wherein said shaft is
provided with a pair of superimposed counterbalance elements, one
of said elements being rotatable with the shaft in one direction
and the other being rotatable relative to the shaft in the opposite
direction, and means for driving the elements in their respective
directions and in timed relationship to reciprocation of said
sickle for counterbalancing inertia forces of the sickle at
opposite ends of its stroke.
13. In apparatus for translating rotary motion into reciprocal
motion:
a single component;
means coupled with said component for driving the same in a
circular path of travel;
a reciprocable member; and
a pair of spaced apart, substantially equal length pitman links
extending in opposite directions from said component and coupling
the latter with said member for reciprocating the member with
substantially equal acceleration and deceleration adjacent opposite
ends of its path of travel upon actuation of said driving
means.
14. In apparatus as claimed in claim 13, wherein said driving means
includes a shaft, said component being eccentrically coupled with
the shaft for orbiting movement about the axis of the shaft when
the latter is actuated.
15. In apparatus as claimed in claim 14, wherein said component is
pivotally coupled with said shaft, said pitman links being disposed
on opposite sides of the pivotal axis of said component.
16. In apparatus as claimed in claim 15, wherein said member is
provided with an opening receiving said component for reciprocation
thereof transversely of the path of travel of said member.
17. In apparatus as claimed in claim 13, wherein said driving means
includes a shaft and said member is provided with a sickle for
reciprocation by the member, said member being mounted for swinging
movement about an axis spaced from said sickle.
18. In apparatus as claimed in claim 17, wherein said sickle is
disposed at one end of said member and said swinging axis of the
member is disposed at the opposite end of the latter.
19. An apparatus as claimed in claim 17, wherein said shaft is
provided with a pair of superimposed counterbalance elements, one
of which is rotatable with the shaft in one direction and the other
of which is rotatable relative to the shaft in the opposite
direction; and means for driving the elements in their respective
directions and in timed relationship to reciprocation of said
sickle for counterbalancing inertia forces of the latter adjacent
opposite ends of its stroke.
Description
This invention relates to the reduction of mechanically destructive
and physically jarring vibrational forces which are normally
induced in mechanisms that translate rotary motion from a drive
shaft into reciprocal motion of a heavy member such as, for
example, the sickle of the implement header.
The problem of reducing vibrations caused by abrupt changes in
direction of a rapidly reciprocating, heavy member at opposite ends
of its stroke has existed for a long time. It is known, for
example, from U.S. Pat. No. 2,428,924, issued to V. N. Albertson on
Oct. 14, 1947, to utilize a pair of superimposed, oppositely
rotating counterweights which are driven to timed relationship to
reciprocation of a sickle in such a manner that the weights
counterbalance the inertia forces at opposite ends of the sickle
stroke. The weights are so arranged that when the sickle reaches
one end of its stroke with its inertia forces headed in one
direction, the inertia forces of the rotating weights are headed in
the opposite direction so that a balancing of forces occurs. Hence,
vibrations are materially reduced.
However, the mechanism of the aforesaid Patent, as well as many
other sickle drive mechanisms of which we are aware, utilizes a
single, relatively short, pitman rod to translate rotary motion
from the drive shaft of the mechanism into reciprocal motion of the
sickle, and, as is well known, a short pitman rod cannot
reciprocate a driven member so that its velocity varies
sinusoidally over the full stroke. Instead, the member driven by a
short pitman rod must stop and start more abruptly at one end of
its stroke than at the opposite end, and this results in the
inertia loading being different at opposite ends of the stroke.
Accordingly, the member cannot be readily counterbalanced because
the weights utilized must be based upon an average of the two
different inertia loadings, not the exact amount of either
loading.
The problem of the single short pitman could be solved by merely
extending the pitman to such a length that the angle through which
it moved during operation would be very small. Then the variance in
velocity over the full stroke would approach sinusoidal and the
inertia loadings at opposite ends of the stroke would approximately
equal one another.
However, as a practical measure, such an arrangement is not
possible on an implement header, for example, because the long
pitman, disposed at one end of the sickle, might extend well beyond
the lateral extremes of the header itself, presenting a dangerous,
unwieldy, and easily damaged appendage to the header.
Accordingly, one important object of the present invention is to
eliminate unequal inertia loading at opposite ends of the stroke of
a pitman-reciprocated member whereby such loading can be readily
counterbalanced by appropriately driven weights in order to provide
smooth, substantially vibration-free operation.
Another important object of this invention is to provide such a
remedy without producing a cumbersome apparatus subject to frequent
mechanical breakdown and hazardous to personal safety.
Pursuant to the foregoing, an additional important object of the
present invention is to provide a pair of short pitmans extending
oppositely from an eccentrically driven component and connected to
a common member to be reciprocated so that the two pitmans
counteract the negative effects of one another while maintaining
their positive effects in order to closely approach reciprocation
of their common driven member sinusoidally.
OTHER RELATED ART
Elements of Mechanism by Doughti and James, 1954, Library of
Congress catalogue card number 54-7373, page 149.
In the drawings:
FIG. 1 is a fragmentary, side elevational view of a sickle drive on
an implement header employing the principles of the present
invention;
FIG. 2 is a cross-sectional view through the drive taken along
irregular line 2--2 of FIG. 1;
FIG. 3 is an enlarged, front, vertical cross-sectional view through
the gearbox of the drive showing the counterbalance weights thereof
in position to counteract the sickle when it is at the left end of
its stroke as viewed from the front of the header, the linkage
below the counterweights being rotated 90.degree. out of position
to illustrate details of construction;
FIG. 4 is a horizontal cross-sectional view through the apparatus
of FIG. 3 looking downwardly from just above the counterweights
when the latter are rotated into diametrically opposed
relationship;
FIG. 5 is a horizontal cross-sectional view through the apparatus
of FIG. 3 looking upwardly toward the bottom of the counterweights
from a point just above the linkage and with the weights rotated
into the positions illustrated in FIG. 4;
FIGS. 6 - 9 are schematic and diagrammatic views of the drive
illustrating the motions of the various components involved with
their positions relative to the counterweights at corresponding
points in the operating cycle; and
FIGS. 10 and 11 are diagrammatic views of the special drive linkage
of the present invention illustrating the relationship of the
pitman links to one another at opposite ends of the sickle stroke
and showing in dashed lines the respective paths of travel of the
links during each operating cycle.
The principles of the present invention, while applicable to any
situation wherein a member is to be driven reciprocably, have been
illustrated in conjunction with the sickle assembly of an implement
header 10. A shaft 12 (FIG. 2) extending across the rear of header
10, is coupled at one end with a prime mover (not shown) and has a
large sheave 14 attached to its other end. The sheave 14 carries an
endless belt 16 that extends fore and aft along one side of header
10 and is looped about a generally cone-shaped sheave 18 for
driving the latter in the same direction as shaft 12. An idler 20
along the lower stretch of belt 16 tensions the latter.
As shown best in FIG. 3, the sheave 18 has a driven shaft 22 that
extends into a gearbox 24 wherein a first bevel gear 26 on shaft 22
meshes with a pair of opposed second and third bevel gears 28 and
30 respectively that rotate about a common axis perpendicular to
shaft 22. Gear 28 is keyed to a generally upright drive shaft 32
extending centrally through gearbox 24 so that rotation of gear 28
in one direction by input shaft 22 is imparted to the upright drive
shaft 32. On the other hand, the other bevel gear 30 associated
with drive shaft 32 is provided with bearings 34 around shaft 32
that enable the gear 30 to rotate in the opposite direction and
relative to shaft 32, such being caused by bevel gear 26 on input
shaft 22.
A sleeve 36 at the bottom of gearbox 24 surrounds drive shaft 32
and is fixed to the gear 30 for rotation therewith in a direction
opposite to shaft 32. Bearings 38 between sleeve 36 and shaft 32
permit such relative rotation. The sleeve 36 has a generally
semicircular weight 40 secured thereto by a series of screws 42 so
that weight 40 rotates with sleeve 36 during operation. A second,
generally semicircular weight 44 is secured by a series of screws
46 to the enlarged, lowermost end of drive shaft 32 in underlying
relationship to the upper weight 40 so that weight 44 rotates with
drive shaft 32 during operation and in a direction opposite to
weight 40.
The weights 40 and 44 are so positioned on their respective
mounting means that, during operation, they come into vertically
aligned relationship with one another when they are in their
rightmost positions viewing FIG. 3, and also when they are in their
leftmost positions viewing FIG. 3. On the other hand, they are
spaced apart to the greatest extent when aligned fore-and-aft of
header 10 as illustrated in FIG. 1.
Returning to FIGS. 1 and 2, a member 48, commonly known as a sway
bar, extends generally fore-and-aft of header 10 along the side
thereof and is swingably mounted at its rearmost end by a pivot 50
for reciprocal or oscillatory movement in a path extending
generally transversely of the normal path of advancement of header
10. The member 48 extends forwardly from pivot 50 beneath gearbox
24 and has a ball-joint coupling 52 at its forwardmost end with a
sickle 54 supported by header 10 for reciprocation transversely of
the path of advancement of header 10.
The member 48 is provided with an elongated opening 56 adjacent its
forwardmost end that provides clearance for the special linkage 58
which drivingly couples member 48 with gearbox 24. Linkage 58
includes a generally elliptical main component 60 that is carried
within opening 56 by a pair of spaced-apart, oppositely extending,
identical pitman links 62, each of which has a first pivot 64 with
component 60 and a second pivot 66 with the member 48 on opposite
sides of opening 56. Both links 62 are of the same length and each
consists of a pair of superimposed elements 68 separated by pivots
64 and 66 as illustrated in FIG. 3.
The center of component 60 pivotally carries a drive stud 70 that
is, in turn, fixed to the lower weight 44 in eccentric relationship
to the drive shaft 32, all as best illustrated in FIG. 3. In this
manner, the component 60 is drivingly coupled with shaft 32.
OPERATION
As the drive shaft 32 is rotated, the eccentrically disposed stud
70 pulls the component 60 in an orbital path about the axis of
drive shaft 32 counterclockwise as FIGS. 6 - 9 are viewed. However,
the pitman links 62 limit component 60 to a purely rectilinear
reciprocal path of travel relative to member 48 within opening 56
and, therefore, a resultant force is created which swings the
member 48 from side-to-side about pivot 50. This reciprocal
swinging or oscillation of member 48 is in turn transmitted to the
sickle 54 through coupling 52 to drive sickle 54 back and forth
across the normal path of advancement of header 10 for severing a
standing crop.
Turning to FIGS. 10 and 11, it may be seen that because the stud 70
moves in a circular path of travel 72 about the axis of shaft 32
during operation, the ends of the pitman links 62 at pivots 64 are
caused to move in their own individual circular paths of travel 74.
Taking the left pitman link 62 in FIGS. 10 and 11 as an example,
and assuming for the moment that the right link 62 is not being
utilized, it will be seen that the link 62 moves through two
extreme conditions corresponding to the opposite ends of the sickle
stroke, the linkage 58 being shown in FIG. 10 with the sickle at
one end of its stroke and in FIG. 11 with the sickle at the
opposite end of its stroke.
More specifically, the left link 62 is shown in FIG. 10 extending
completely across its path of travel 74, representing one extreme
condition, while the left link 62 is illustrated in FIG. 11 as
approaching its path 74 and disposed primarily outside of the
latter, this being the other extreme of the link 62. Because pivot
66 of the left link 62 is the point at which force is transmitted
from linkage 58 to member 48 and such point moves generally in a
straight line toward and away from the side of header 10 as the
component 60 orbits about the axis of shaft 32, the link 62 swings
back and forth through an angle (as shown in FIGS. 6 and 8) while
its pivot 64 moves about path 74. Because of this geometry, the
pivot 66 stops and starts more abruptly as left link 62 approaches
and leaves the condition illustrated in FIG. 11 than when it
approaches and leaves the condition illustrated in FIG. 10. Hence,
the driving force imparted to the member 48 by the pivot 66 is
different as the member 48 approaches its opposite extremes,
resulting in a tendency to make the inertia loading of sickle 54
different at the opposite ends of its stroke.
This behavior is inherent in drives where a short pitman is
utilized to transmit rotary motion from a crank into reciprocal
motion of another member. Because the short pitman must swing back
and forth through a substantial angle during actuation by the
rotary crank, the driving end of the pitman inherently has a "fast"
extreme and a "slow" extreme, the pivot 66 of left link 62 being in
its "slow" extreme in FIG. 10 and in its "fast" extreme in FIG.
11.
The inherent deficiencies of a single short pitman, such as the
left link 62 of FIGS. 10 and 11, can be overcome by the addition of
a second short pitman link which is so arranged that its driving
end is moved through its fast extreme while the driving end of the
first link is moving through its slow extreme, and vice versa.
Thus, the right link 62 of FIGS. 10 and 11, while seemingly at the
same point in its path 74 as the left link 62 is on its path 74, is
actually disposed to move its pivot 66 through the fast portion of
its cycle while the left link 62 moves its pivot 66 through its
slow portion. Therefore, when pivot 66 of the left link 62, for
example, begins to slow down, the "slack" is picked up by the pivot
66 of the right link 62, which is just beginning to speed up, the
result being that the member 48, and hence the sickle 54, has the
same rate of acceleration and deceleration through both halves of
its stroke. This means that the velocity of sickle 54 will vary
substantially sinusoidally, causing the inertia loading at one end
of the sickle stroke to be equal to that at the opposite end.
Hence, the inertia loading can then be readily counterbalanced
through the weights 40 and 44, whose sequence of operation relative
to the linkage 58 may be most easily understood by referring to
FIGS. 6 - 9.
Beginning in FIG. 6, the weights 40 and 44 are disposed at opposite
fore-and-aft extremes in order to cancel out one another when
member 48 is in midstroke, such median position being illustrated
by the broken line 76. When the member 48 is shifted to its
rightmost extreme, viewing the front of header 10, the weights 40
and 44 are disposed in superposition with one another at their
leftmost extreme (viewing the front of the header 10) as
illustrated in FIG. 7. Thus, the weights 40 and 44 supply a
leftwardly directed inertia loading of their own that cancels out
the rightwardly directed inertia loading of member 44 and sickle
54.
Then as the member 48 and sickle 54 are returned to midstroke as
illustrated in FIG. 8, the weights 40 and 44 are again separated
fore-and-aft of header 10 to balance out each other and not supply
any resultant inertia loading.
Finally, when the member 48 and sickle 54 reach the opposite
extreme of FIG. 9, wherein sickle 54 is in its leftmost extreme
viewing the front of header 10, the weights 40 and 44 are brought
into superposition in their rightmost extreme viewing the front of
header 10 to supply a rightwardly directed inertia force which
cancels out the leftwardly directed inertia force of member 48 and
sickle 54.
Thus, the result of the special linkage 58 and weights 40 and 44 is
a smoothly operating, well-balanced and substantially
vibration-free sickle drive that materially reduces the likelihood
of mechanical failure caused by induced vibrations. Moreover, the
drive is relatively compact and allows higher operating speeds to
be achieved than heretofore possible without the usual vibrations
and shaking which normally accompany such higher speeds.
* * * * *